so you could try same play looking for contents of
comint-dynamic-complete-functions
I obtain (in both cases):
comint-dynamic-complete-functions is a variable defined in `comint.el'.
Its value is
(comint-c-a-p-replace-by-expanded-history shell-environment-variable-completion
shell-command-completion shell-c-a-p-replace-by-expanded-directory
pcomplete-completions-at-point shell-filename-completion
comint-filename-completion)
Local in buffer *shell*; global value is
(comint-c-a-p-replace-by-expanded-history comint-filename-completion)